Well drilling composition and method of manufacture thereof



Patented Aug. 25, 1953 BEST AVAiLABLE COPY OFFICE WELL DRILLINGCOMPOSITION AND IHETHOD OF. MANUFACTURE THEREOF 'HenryWJ-Rnhn, CorpusChristi, Tex.

-Application Aprilvzl, 1953, erial No. 349,993

'22Cllims. (Cl-H.

This invention relates to a well treating composition suitable for usevin well drillingffluids and'has particular relation to theirapplication to drilling oil and gas wells.

In such uses, amud laden fluid is nsed'inrotary drilling or such wells.The fluid -is.pumped down through the drill system to the bit and thenflows upward in the annular space between the drill stem and the wallsof the bore .hoie. The-fluid-servesseveral purposes. It carriesouttingsandsand, working in at the base oi the bore hole, to-settlingareas-where these cuttings and'rockparticles-settm out. Gas comingiromthelbore hole:and'entrained in .the fluid blibble out in thesettlingarea. The'fluid isthen pumped 'backto the'driil stem and thecycle is repeated.

Another function or. the fluid is to cool .and

lubricate the bit. .The'fluidfalso seals the walls suspension to impartto .the mudalhighdensity sumcient to produce adequate hydrostaticpressure. Also, the. colloidal nature or "the mud .makes it moreeflectivein plastering :the walls .01 the borehole to seal o'flporousiormations'and ftosssist'inoarrying cuttings out n! the :hole.

Toomucneolibidal material renders the fluid too viscous. thereby makingit 'diflicult to ',pump. 'Onthe other hand. fluids made 'irom'clayshavingja deficiency or colloidal material must 'be improved byaddition.of hixhlyeolloidail clay suchasbentonite. .Itis desirable that the fluidpossess 'thixotropio properties in order that the cuttings-no notsettle-end clog the bore hole in. or temporary suspensions in theoperations. v Imadditiomthe drillingifluidsometimes must .eombatvrorma'tions .known as jheaving shale. H viue=shale.'ie.believedtobeeaused .by the hydration or shale particles withwateriromthe.ordinarydrillingnuidse Jtishighly s'ensitiveto waterandhighlycollcidal.Theshaleswells, du- -integrates,andflows into thehore hole, ottenelossintthedrillingtools.

-Ordinarr-drilling fluidse-re oreatedby using'-water-as=the'llquid.dispene phase and eomblnin: with-it mud-or claysirom-the .bore tosether with additional material capableot impel-tinsadvantageoumpropertiee-to the fluid.

According to the :present invention. .a novel and a novel method oiproducing such composition has been provided. This composition comprisesthe-reaction product of tree bark, preferably in a'shreddcd orpulverulent state, with sodium hydroxide or like alkali metal hydroxide.The composition may or may not contain other components such as-ireealkali metal hydroxide and solid'inert diluents, for-examplecalcium-carbonate and the like.'ali as more 'fully set forthhereinafter. V

The composition which is contemplated herein may be-preparedaccordi'ngto this invention, by dispersing tree bark containing the desiredconcentration (10% or more) -01 natural tannins therein in aqueousalkali metal hydroxide solution and'heating the solutiontoan'elevated'temperature to dehydrate the mixture. During -the dehydration,digestion ot the tannates as well as other bark components and reactionsof an unknown character occur. 'This =di'ges'tlon and/or heating appearsto exert certain advantageous influences as will 'be explained morefully hereinaiter. The advantageous characteristics'which arethusachieved may be-du'eto partial-oxidation oi'theproduct during heating,to 'morethorougli reaction of the-sodium hydroxide with the tannate,tomodiflc'a'tion 'oi the 'tannate molecule. 'to reaction oi'non-"tanninsin the bark and/or to other causes.

'I'hecomposition thus obtained is valuable as a drillingfluiclad'ditiveeinc'e itis 'in the iorm'oi a 'dry, pulverulent powderwhich remains in a pulverulent state even under conditions of highhnni'dity. It is convenient"to handle and may .35 beuse'd. withcomparative safetyby drilling crews without the danger of burns and likeinjuries and without 'excessive wastage. Furthermore, the composition'thus produced disperses quite readily in drilling fluids-and is lessexpensive to so use than-comparable-conipositions@produced fromisshredded-or otherwise broken up"int'o chips "having; thickness,preferably less than of an inch. TZheee chips are then'introduce'd intoa solution or an alkali metal'hydroxide, such as aqueous sodiumhydroxide.

Frequently. the'bark is broken up by fl assing .it through a hammer millor like conventional means tor grinding .or shredding the bark and theresulting productis dumped into an aqueous sodiumhydroxide solution.'This'solution is then :welltreetingeomposition has been produced.heated toe. temperature approximating its boil- BEST AVAiLABLE COPY ingpoint and maintained in that condition to bring about a disintegrationof the bark structure. The resulting hot solution is delivered to asuitable drying equipment, such as a drum, tray or spray dryer where thematerial is dried to a solid state; at room temperature this product isdry to touch but may or may not be completely anhydrous.

Where the alkali metal hydroxide content of the produce is high, it isadvantageous to incorporate a solid diluent in the mixture prior todrying. Unless such solid diluent is incorporated, it often is foundthat such mixtures, during drying become sticky and do not dryeffectively. On the other hand, when such diluents are used. little orno caking of the product is observed during the dehydration and a driedproduct which shows little tendency to agglomerate on standing isproduced. Calcium carbonate has been found to be an especially effectivediluent for this purpose. Other typical materials which are suitableinclude calcium hydroxide, barium carbonate, magnesium carbonate, andother alkaline earth carbonates or hydroxides, metal oxides and likeoxides, includingzinc oxides, titanium dioxide, silica, calcium oxide,magnesium oxide, silicates such as precipitated magnesium silicate, orlike alkaline earth metal silicates clay, including bentonite clay,kaolin, montmorillonite. fuller's earth, or like adsorbent clay, bariumsulfate, calcium sulfate, lamp black, gas black. and other carbonblacks. Such diluents possess absorbent characteristics which tend toimprove the product.

For most p rposes, it is desired that the inert solid diluent beessentially insoluble in water. This is not absolutely necessary sincesoluble diluents can be used to prevent the agglomeration and thecakingwhich occurs during drying. Thus, sodium carbonatemay be used forthis purpose. On the other hand, it is generally found advantageous toutilize a diluent which has alow water solubility (below 1% by weight)since, otherwise, the diluent may have an adverse effect upon thedrilling fluid. Furthermore, it is preferred that the; diluentbe-non-hygroscopic in order that the product, once dried, remain in apulverulent state.

The diluent should be relatively line to permit ready dispersionthroughout the composition. Generally, diluents having a particlesizebelow about 20 mesh.will be satisfactory.

The amount of diluent which may be present will vary in accordance 'withthe type ,of bark used. Thus. where the woody and. fibrous con-' tent ofthe bark is high as in the case of mangrove and wattle barks, thediluent may be low and frequently eliminated. On the other hand, barkshaving high tannin content or high extractable contents and low fibrouscontent generally require an appreciable amountof diluent. Likewise,compositions containingsmallamounts of alkali metal hydroxide do notrequireas much diluent as do. compositions containing large amounts ofalkali metal hydroxides. Thus. diluent concentrations of 5 to 50 percentby weight of the alkali metal-hydroxide and bark in the composition areused wherenecessary. Larger amounts of diluent usually are unnecessaryalthough they rarely exert an adverse effect. The amount ordiluent usedseldom exceeds twice the tannin and to produce an alkaline product. Itwill be understood that a bark such as mangrove or wattle bark containsa number of components including fibrous material, water solubletannins, water soluble non-tannins. lignins, etc. The amount of tanninin such barks may be determined readily by extracting the bark withwater and titrating the solution by standard methods. The amount ofalkali metal hydroxide should be in excess of that required to reactwith the tannin in the bark. When further alkali is present it can reactwith other bark components such as the non-tannins, lignins, etc. Thus,these components which are not normally active are made active by thetreatment herein contemplated.

The exact amount of alkali metal hydroxide used varies with the barkswhich inevitably vary in composition. To achieve optimum results about 1to 5 parts by weight of bark is treated per part by weight of alkalimetal hydroxide. However, larger and smaller amounts of alkali metalhydroxide can be used although it is rare that more than about 12 partsof bark are used per part of alkali metal hydroxide. Moreover, it israre that the amount of alkali metal hydroxide will exceed two to fourparts by weight 01' sodium or equivalent hydroxide by weight of bark.These amounts of alkali metal hydroxide produce a product, a 2% watersolution of which has a DH of about 9 or above.

Where the amount of alkali metal hydroxide used is high (above about 1NaOH to about 5 of bark in the case of mangrove bark) the resultingproduct contains free alkali metal hydroxide, and such larger amountsoften are advantaaeous.

Alkali metal hydroxide solutions of any convenient concentration may beused, so long as the solutions are liquid. Preferably, solutionscontaining 5 to per cent by weight of NaOH are used. More concentratedsolutions may be used but are so viscous that diiliculty is frequentlyencountered in handling the resulting products. On the other hand, moredilute solutions are, ob- Jectionable because of the large amount ofwater which must be evaporated.

.As previously stated, the aqueous mixture or slurry of alkali metalhydroidde and tree bark is digested at a temperature approximating theboilin: point and then evaporated to dryness. This dehydration iscontinued until a produce which is substantially dry to touch at roomtemperature is produced. Such product may contain as alkali metal amountof alkali metal hydroxides and alkali metal tannate in the composition.

The amount of alkali .metal hydroxide used much as about 18% byweight oreven more of moisturefalthoush the. composition preferably has amoisture content somewhat below 25% by welshthHT rj'.

The process herein'described has been found to be especiallyadvantageous in that it imparts improved properties to the compositionwhich are not achieved. simply by mixing the bark with hydroxidesolution in the cold. Thus, it has been determined that acompositionwhich has been produced according to the present invention moreeifectively reduces the viscosit of drilling muds thando comparablecompositions formed by mixing bark with alkali metal hydroxide in thecold. Furthermore, the compositions produced according to the presentinvention are more readily soluble and dispersible in fluids than arecompositions formed by simple mixing in the cold.

These advantageous results are achieved to a large degree by virtue ofthe heat applied to the should be at least suillcient to'react with the7 mixt re ur ns he dryin -en uring dises n BEST AVAILABLE COPY asse s-aspriorto drying and it'appears that a substantial reaction takes placebetween the reaction components. The-rate at which this reaction occursis influenced appreciably by the temperature of heating, the reactionbeing more rapid at high temperatures than at lower temperatures.

In general it is found best to effect at least the final states 0!heating of the composition at a temperature above about 100' 6.,preferably 150' to 350' 0., but below the temperature at which barlccomponents pyrolyze. A relatively short period 'of' such heating,- forexample, 30 seconds to several minutes is permissible. 0n the otherhand, baking for several hours at an elevated temperature often producesfurther improvement in the properties of the product. The temperature ofthis heattreatment should not be excessive; Temperatures of' above about100' 0., preferably l50-to 350' (7., normally aresuitable.

6 shells and like fibrous products which contain tannin may be used.

The tannin or humic acid content of such components should not be undulylow and in most 8 cases it' is desired to use materials containing inexcess of about 10 percent of tannin and/or humic acid.

If necessary, standard anti-foaming agents and anti-fermenting agentsmay be incorporated if desired. Normally no objectionable amount of foamis produced in use of a composition of the type herein contemplated inwhich a bark, such as wattle bark, is a component. On the other hand,agents which tend to cause foam sometimes are present in barks. If suchagents are in. concentrations such as to make foaming a seriousproblemin oil well drilling, typical antifoaming agents may be added to thecomposition, such as linseed oil, cresol, octyl alcohol, castor oil Atlowertemperatures much longer periods of'20 and like anti-foamingagents. Furthermore,

heating are required to achieve equivalent results. Prior to drying to asolid. product digestion of the bark-alkali metal hydroxide solution isadvsntageous in order to insure relatively complete reaction. Thisdigestion maybe conducted over a period of minutes to 24 hours, usually1 to 8 hours aira temperature of about 75 to-loo' C.

The product after drying is a dry pulverulent brown toblack'solid'whichis the reaction prodnot of thesodimn hydroxide with the bark'and/or itscomponents It sppears'homogencousto the eye and is readilydispersedoridissolved in water. It is in a granular form andforconvenience usuallyis reduced to a particle size where a preponderantamount (90%" or more) will pass through a 10 mesh screen.- i r Theproducts produced as herein contemplated I are especiallyvaluablebecause of their hish content or tanninand-also-becsuse the lisnins andother materials not normally active are made" active bythe-treatmentherein contemplated.

when: a'product prepared from. a bark such as wattle or mangrovebsrkaooording to this inventionis; dissolvedin. water, .the resultingsolution exhibits little-tendencyfor the bark ilbers andcorporationrofcthercomposition'intor a. drilling. brmaldng a: solutionoaths: herein.

oontemplateitnovslicomposition. beiorshand-and introducing. thissolution. at m slom' oontinuous some barks and fibrous materials containappreclable concentrations of sugars, and like carbohydrates. In thatcase, drilling fluids in which these compositions have been incorporatedsometimes evidence a tendency to ferment, particularly where the pH ofthe drilling fluid is below about 10. In such case standard agentscapable of inhibiting fermentation may be incorporated.

The drilling fluid compositions herein described are capable of use withvarious types of drilling fluids. Commonly used drilling fluids aspreviously noted, comprise an aqueous fluid suspension of clay, usuallyincluding an appreciable amount of.' bentonite or like type of 'claywhich swells readily and which forms a thixotropic suspension. Such amud may be loaded with other weighting agents including barytes, ironoxide sndlike materials if desired. The compositions hereirrdescribedare particularly useful-in the 40 treatment of muds of this character.However,

various other muds may be treated by these compositions.

An-eiiective mud which has been found to be especially suitable for deepwell drilling is obtained by a treatment of bentonite or like clays withcalcium compounds to base exchange the naturally occurring sodiumcontent of the hentonits or like clay with calcium to form what iscommonly called calcium bentonite. Muds containing such calciumbentonite have been found toibe quite effectivein deep well drilling.The compositions herein described and claimed are ;very elfective in thetreatment of such muds.

in addition; itis not uncommon to use adrillfletflintwledimmumwmchmmfimd ywater emulsion. -Because of thenatural tendother outlets drflflnrfluMF-PMW" '3 ency of elite settle outfrom water, it is necesw his -mwi nstvsluableare obtainedwhen. insuch-cases to useemulsifying agents to ansrove or watt e bark sre-t eatdw ccause the oil'to disperse in the form of a stable tot s'procssiThunmangrovebarkwhicheon-sso emulsion. .Moreover; it is'important thatmud ;tains less tannirrpezpcundthan-euebracho'sx treatingagentsused inconnection with such oil tractinatbetreated-aceordingtdthiiinfentiondrillinglfluids be ot a character such that they and used on an equalweight basis inplaceotithe more expensive quebracho-cxtrsct.

may be used lathe samem .1 a z 85., have been found to effectivelystabilize the emul- It willi alsobe understood thatother barkx are-isuitable for the WW 11min c011- templated; m examplaredwood bark been"ioundito be dflddflm Moreover; other-barks in-' looks bar: sprucebark}.- n: bark; andciikc whole bsrksi commonlrueodw '0' source os'tsnnimin sionandthus have the advantage of permitting ;the.use of lessemulsifier or-even permitting the Ielimination of'the emulsifier. Thiseliminates or-minimizes the requirement for specially preciudingpine'ibamahsstnutbarkoabbsrtchempared expensive, emulsions and permitsthe use of'dllcaper base oils which'are commonly availzsbleindrillingareascwlt haszbeen-iound that the tendency of thecompositions-herein contemm y be used-according thisinvsntiona Moseplated to stabillze i emulsions is markedly. envm seed osrsndotbcr wood;pecans hanccd byths drylngsandlor baking operation.

BEST AVAILABLE COPY That is, when wattle bark or like bark is simplydispersed in alkali metal hydroxide solutions little tendency towardemulsiilcation is observed. n the other hand, by producing the wattlebarksodium hydroxide product according to the process described herein,the resulting product is a much more eifective emulsifying agent thanthe simple mixture of the bark and the solution. This has also beenfound to be the case when extracts such as quebracho extract, wattleextract, and like tannin extract are used in lieu of the bark.

The following examples are illustrative of the invention.

EXAMPLE I A milk of lime slurry was made up containing 322 grams perliter of calcium oxide in the form of calcium hydroxide. This slurryalso contained approximately 25 grams per liter of calcium carbonate.Four hundred pounds of ground wattle bark, 332 pounds of'an aqueoussolution of sodium hydroxide containing 50% by weight of sodiumhydroxide, 133.2 pounds of sodium carbonate were mixed together withsumcient of the milk of lime slurry described above to introduce 70.2

pounds of calcium oxide into the mixture. This mixture was boiled withstirring to eifect a solution of the soluble components thereof at atemperature of approximately 90 to 100' C. Thereafter, the resultingmixture was fed directly to a drum dryer which was heated directly bysteam at a 100 pounds per square inch gauge pressure. Thus, the heatingtemperature was approximately 170' C. The product undergoing dryingremained at thiselevated temperature or closely thereto for severalminutes. This material was then put through a hammermill in order togrind it to a size which would pass approximately a mesh screen. Theresulting product was a black, granular product which contains about10.4% by weight of moisture.

The following table indicates the amount of reduction 17-. viscositywhich was achieved by adding various amounts of the resulting wattlebark product to a synthetic drilling fluid prepared by concentratingnatural shale mud obtained from an oil well in the Borresas Field inTexas to a viscosity of centipoises.

Viscosity,

lcnndscflrodnotlsrlen'eloflud 0mm "attend 50 grams of wattle bark whichhad, been previously hammer milled to reduce the size of the wattle barkto below 10 mesh was added to 83 grmns of aqueous sodium hydroxidesolution containing 50% by weight of NaOH. The product" was thoroughlymixed and then dried at 190' O. for three hours. This producteffectively reduced the viscosity of standard muds when addedthereexams: in

Two hundred pounds of shredded redwood bark produced by paasingredwoodbark through a hammer mill were added to aslurry con v tainlng 133pounds of a caustic solution containing 50% t",

8 by weight of NaOH. Fifty pounds of commercial sodium carbonate and 64pounds of C (as a milk of lime suspension containing 318 grams per literof active CaO and 18 grams per liter of calcium carbonate), were addedto the mixture. The mixture was stirred strongly and heat applied bydirect and indirect application of steam to raise the temperature of themixture to about to C. During this heating, sufllcient water was addedto dilute the slurry to a degree sufllcient to permit ready delivery ofthe mixture to a drum dryer by means of a centrifugal pump and also topermit efllcient drying upon the drum The feed liquid was thus fed to adrum dryer in which the roller speed of the dryer was 2 R. P. M. and theroller temperature was about C. (the temperature being established byvirtue of steam supplied to the roller or drum at 100 p. s. 1. gauge).After drying, the product was ground to a uniform coarse particle sizeby means of a hammer mill. Analysis of the ground product showed amoisture content of 9.7 by weight,

a calcium content of 9.9%, computed as calcium carbonate, and anavailable alkali content, based upon titration with methyl orange andcorrecting for calcium carbonate content oi 37.3 expressed as NaOH.

Tests were made with this material using a mud of the type described inExample 1. The following data summarize the results obtained:

Viscosity reduction Viscosity in Lbs. Product Bbl. Mud CentiDO SQEXAMPLEIV 82 grams of peeled pine bark was mixed with 82 grams of'anaqueous caustic soda solution containing 50 percent by weight NaOH andenough water was added to permitcomplete dispersion of the bark andcaustic. The mixture was taken to dryness and then baked in an oven for20 hours at -185 C. The baked product weighed 88.6 grams. The followingtable illustrates-results obtained when this product was addedto s. mudobtained from the Paso Ancho -55Oil Held in Texas which had beenconcentrated to 80*eentipoises.

' Viscosit in 2 oundslsoduetperbsrrelofmud Campos e0 61 55 L7 26 l9 1312 11 0 EXAMPLEV 700 gallons of aqueous sodium hydroxide solutioncontaining 50% NaOH by weight was mixed in a mixing tankvwith 2500gallons'of water and the resulting solution was heated to 212 F. 2000pounds of; mangrove bark containing 30% by weight of tannin (determinedby the Loewenthal BEST AVAILABLE COPY "zoom-toe Proctor-method wasadded! slowly. tothe hot solution over a period of 8 hours whilemaintainmy the temperature'ofi the mixtureat 212 F. by introduction: onsteamtherein. Following the addition, the mixture was digested for 10hours at' about 220'. 7. Thereuporr- 4000- pounds of li'gnitecontaininszabout 37%byweight of humic acid was: addedtto'the =mixtureand=the mixture was further digestedifon 2: hours at' 220' r.Follcwingzthis theimixturenwaswied to 'a pair of drum: dryers having:theiriaceespaced approximately mofl inchapart. and heated by dry steamat wpressure ottise poundsper square inch. In this-wayraproduct-havingzs granular character wasproducede. a

other compositions may: be prepared in a mannersimilarrtoithe-methodsoutlined in: the

aboveexamplesa: a

Typical; compositionslwlnch may-be prepared in this manner include thefollowing:

' Parts'byweight Sodium hydroxide. 150 Wattle bar 80 Sodium hydr 100Redwood bar 200 Sodium hydroxide 100 Wattle-har s 150' Calciumscarbonate.i........ 40 Sodium: hydr -100 Redwood; bark ilgg Calcium: carbons Itwill-be observed that-irequently mangrove, redwood, and like barksdo-notrequire-introduction' oi further-solid diluent'because oi thefibrous content thereofi To a" large extent, the requirenienbot iurthetdiluent dcpends to a-dezree upon :the' contentiofithe tannin inithe barkand alsoiupomthe. modeioi: drying:- used; Whena drum dryer: is used, itis oiten advantageous-to use rsome' diiuenhisuclr as calciumscarbonateor like diluent: as. listed! above in order to prevent coking: om withothen methods of drying such; diluents may be necessary. The in situprecipitation. ct CaCOa by causticization or sodium carbonate with limeis a convenient means of providing diluent needs while simultaneouslyfurnishing some oi the sodium hydroxide requirements."

While the invention has been described with particular reierencetosodium hydroxide, it is to be understood that other alkali metalhydroxides also may be-used. imlieu. of, or inponiunction with,sodiunthydroxide. Typical alkali metal hydroxides include potassiumhydroxide and lithium; hydroxideer However, best results areobtainedwherr sodiumhydroxide is used. It' is also to be understood".that while. the compositions herein describetlc'have been referred to aswell treatinarcompositionmtheymaybe used for other purposes asdotexample in. boiler compositions.

my copendinc applicatiornserial nos.- 114,461,

filed September'l; i949- and 169,781 nled June 22, 1950, the latterhavingnowbeenabandoned.

What is claimed: 1. A method of. preparing a composition which tannin;containing bark and sodium hydroxide in an amount inexcess of that whichwill' react with the -bark components, .andh'e'atin'gthe mixtureat-atemperature above C. but below a-temperature at which substantialpyrolysis oi the bark components cccurs untila' dry product isobtained.v

2. Amethod'oi preparing acomposition'whieh comprises forming. an aqueousdispersion or wattle bark andsodium hydroxide in an amount in excessot'thati which will react with'the-bark componentspand' heating themixture at a temperature above 100 C. but'below a t'emperature atwhichsubstantial-pyrolyns oithebark componentsoccurs, until'a dry'product is obtained.

3L-Almethodo1 preparing a composition which comprises forming an aqueousdispersion'of ba'rk, sodium hydroxide in an'amoun't'in'ex'cessoftliatwhich will react-with the tannin in the bark; and aminert-solididiluent, andheatin'g'tlie mixture at a temperature above 100 C'. butbelow atomperature atwhich substantial pyrolysisof the barkcomponent'soccurs,v.until a dry product is obtained.

4; method accordingto claim BwhereIr'i the inert diluent'is calciumcarbonate.

5.- Alwelltreatingoompositionwhich comprises the reaction product 01tree barkand sodium hydroxide which has beenprepared by heatingtreebarkwith' 0.2' 'tod'parts-by. weight of sodium hydroxide in' theform of an aqueous solutionof sodium hydroxide containing 10 to 50 percent by weight ot-sodium hydroxide at' a temperature above 1m)CItb-vaporize water therefrom and to qbtaina solidiproduct.

6. The composition oi'cla'iin'S'whetein the temperature otldryinaisl50'fto 350 C;

'LXA' method'otiprepa'ring awed-treating, com position' whiclicomprisesforming an aqueous dispersion'oiltree bark containing. atlastlll percentbyweight'oftannin and a sodium hydroxide solution containing l0"to50'percent'by weight of sodiumhydroxide the amount ofsodium'-hydrox-'-ido'bein'g in excess of'th'at required-to react with the tannin in thebark and heating'the mixture atatemp'erature'aboyelflfl"CI; but belowthe temperature at whicl substantial pyrolysis of the bark componentsoccurs, until a solid product is obtained.

8. The process oi claim 7 wherein the amount or 1 to 5 parts by weightor tree bark is used per part or sodium hydroxide.

9. A sclid, granular well-treating composition comprising the reactionproduct or alkali metal hydroxide and tree bark which has been producedby heating a mixture or alkali metal hydroxide the amount of alkalimetal hydroxide being in excess of that required to react with thetannin in the bark, water, and tree bark at a temperature above 100 C.,but below a temperature at which substantial pyrolysis of the barkcomponents occurs.

10. A solid, granular well-treating composition comprising the reactionproduct 01 alkali metal hydroxide andtree bark which has been producedby heatinga mixture or alkali metal hydroxide the amount 0! alkali metalhydroxide being in excess 0! that required to react with the tannin inthe bark, an inert solid diluent. water, and tree bark at a temperatureabove 100 C. but below a temperature at which substantial pyrolyais o!the bark components occurs.

11. A solid, granular well-treating composition comprising the reactionproduct or alkali metal comprises iorming an. aqueous dispersion o: a 7hydroxide an tree bark which has been pro- BEST AVAILABLE COPY duced byheating a mixture. or alkali metal hydroxide the amount of alkali metalhydroxide being in excess of that required to react with the tannin inthe bark, nnely divided calcium carbonate, water, and tree bark at atemperature above 100' 0., but below a temperature at which substantialpyrolysis oi the bark components occurs.

12. A solid granular well-treating composition comprising the reactionproduct of sodium hydroxide and tree bark which has been produced byheating a mixture of sodium hydroxide the amount of sodium hydroxidebeing in excess of that required to react with the tannin in the bark.water, and tree bark at a temperature above 100 0., but belcw atemperature at which substantial pyrolysis of the bark componentsoccurs.

' 13. The composition of claim wherein the giluent is finely dividedalkaline earth metal caronate.

14. A solid, granular well-treating composition comprising the reactionproduct of sodium hydroxide and wattle bark which has been produced byheating a mixture of sodium hydroxide the amount of sodium hydroxidebeing in excess of that required to react with the tannin in the bark,water, and wattle bark at a temperature above 100' C., but below atemperature at which substantial pyrolysis of the bark componentsoccurs.

15. A method oi! preparing a composition which comprises forming anaqueous dispersion or tree bark and an amount or alkali metal hydroxidewhich is substantially in excess of the amount required to react withthe tannin in the bark and. heating the resulting mixture at atemperature above about 100' 0.. but below the temperature at whichsubstantial pyrolysis of the bark components occurs, until a dry productis obtained.

16. The method of claim wherein the bark is mangrove bark.

1'7. The method of claim 15 wherein the bark is wattle bark.

18. The method of claim 1 wherein the tree 12 bark contains at least 10percent by weight or tannin.

19. The composition of claim 15 wherein the tree bark contains at least10 percent by weight 01 tannin.

20. The method of claim 15 wherein the alkali metal hydroxide is sodiumhydroxide and the temperature ,of heating is 150 to 350 C.

21. In a process for drilling a well with well drilling tools whereinthere is circulated a waterbase drilling mud containing clayey materialsuspended in sufilcient aqueous medium to render the same clrculatable,the method which comprises admixing with said mud and interactingtherewith the composition produced according to claim 15 in an amountsufllcient to adjust the viscosity oi the mud and to maintain the mud ina circulatable state, and circulating the resulting mud through the wellduring drilling thereof.

22. The process of claim 9 wherein the sodium hydroxide bark mixture isdigested at to C. before heating above 100 C.

HENRY W. RAHN.

References Cited in the file of this patent UNITED STATES PATENTS OTHERREFERENCES Rogers, Composition and Properties oi Oil Well DrillingFliuds, 1st ed., pub. 1948 by The Gulf Psizblishing Co. of Houston,Texas. Pages 291 and 2 Stern. Role of Clay and Other Minerals in OilWell Drilling Fluids. Bureau of Mines Report oi Investigations No. 3556.Page 68, February 1941.

1. A METHOD OF PREPARING A COMPOSITION WHICH COMPRISES FORMING ANAQUEOUS DISPERSION OF A TANNIN CONTAINING BARK AND SODIUM HYDROXIDE INAN AMOUNT IN EXCESS OF THAT WHICH WILL REACT WITH THE BARK COMPONENTS,AND HEATING THE MIXTURE AT A TEMPERATURE ABOVE 100* C. BUT BELOW ATEMPERATURE AT WHICH SUBSTANTIAL PYROLYSIS OF THE BARK COMPONENTSOCCURS, UNTIL A DRY PRODUCT IS OBTAINED.